1. Field of the Present Invention
The present invention relates to a substrate handler and methods of using same. The present invention extends to device manufacturing methods using a lithographic apparatus which in part comprises the substrate handler.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays (FPDs) and other devices involving fine structures. In a embodiment of the present invention lithographic apparatus, a patterning means, which is alternatively referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device), and this pattern can be imaged onto a target portion (e.g., comprising part of, one or several dies) on a substrate (e.g., a silicon wafer or glass plate) that has a layer of radiation-sensitive material (resist). Instead of a mask, the patterning means can comprise an array of individually controllable elements, which serve to generate the circuit pattern.
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. The substrate is secured on a substrate exposure table or stage, during a scanning process. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
Substrates that are to be irradiated on the substrate exposure table are stored in a substrate storage area or track, and are then moved by a robot or a conveyor to a substrate handler. The substrate handler is adjacent the substrate exposure stage and is used to transfer a substrate directly to and from the exposure table. Known substrate handlers are capable of handling only one substrate at the same time. However, such substrate handlers that are capable of handling only one substrate at any one time have the disadvantage of only being able to pick up and/or put away substrates, i.e., the substrate handler can put an exposed substrate away before it can pick up and load an unexposed substrate. During these handling movements, the parts of the lithographic apparatus involved with irradiating substrates, are sitting idle. In addition, the time necessary for these movements by the substrate handler depends on the layout of the lithographic apparatus, and the demands of the user, and so is difficult to control. Hence, a major problem with known substrate handlers is that the throughput of a single stage machine (such as FPD machines) suffers on account of the delays associated with the handling time of the substrates.
A further problem associated with known lithographic apparatus is that the handling stage of the apparatus consisting of the substrate handler is located next to the exposure table. This gives the apparatus a “footprint” penalty, i.e., the total floor area occupied by the apparatus is large. A problem with having a large footprint is that the apparatus can be contained within a large frame structure that requires many cover plates, and requires a complicated network of wiring. This results in high manufacturing costs, which in turn increases the cost of the final product. In addition, the total weight of the apparatus is high, and is therefore difficult to move about.
Therefore, what is needed is an apparatus and method using a substrate handler which can function more efficiently. What is also needed is a method of manipulating substrates in a lithographic apparatus.